Thanx a lot for your comment orbital!!
You basically said what i was thinking about for a long time now.
The drawings look nice but to colorless. I've already tried to get a deeper spectrum into my drawings - lets say i'm still trying to.
The first two drawings of the topic are one and two weeks old - the other ones are three years old (and they were a lot more grey i think).
I'm using standard pencils (HB, 2B, 4B, 6B) and a technical pencil but got a cretacolor lead holder and coal and graphite leads two weeks ago (a present from my girlfriend). The only problem is i'm not really familiar with it yet.